Две половинки

Shin'ichi Nagakawa and Yuuki Sanada are both involved in an accident and die together. However, they are given a chance to live again. God lets them live for seven more days, but after their time is up, one of them must die again. Oh, and there's one more catch. God decrees that their lives will be shared, including emotions (guilt) and physical sensations (pain). They are also unable to leave one another's side. What will happen during those seven days? Originally a oneshot in 1996, included in the Love Letter collection.